The present invention concerns a reconstruction implant of predetermined shape, of the type having a deformable external envelope containing a filler liquid whose viscosity is substantially equal to that of water.
Such implants are used in humans to replace a gland whose ablation has been rendered necessary by disease or accident, for example. Such implants are intended in particular to replace a testicle or a mammary gland.
Other reconstruction implants of the aforementioned type are used to replace a damaged muscle or for artificial augmentation of the apparent volume of a muscle.
Prior art testicular implants generally have a deformable outer envelope of cross-linked silicone. This envelope defines a closed housing in which a silicone gel is confined.
In prior art implants the thickness of the envelope is in the range from 0.4 mm to 0.7 mm. In practice the envelope is as thin as possible, the consistency of the testicle being obtained by the viscosity of the gel contained in the envelope. The viscosity of a gel of this kind is in the order of a few Pascal.seconds.
Because of the poor public image of silicone gel, implants, and artificial testicles in particular, have been filled with physiological serum instead of silicone gel.
The viscosity of the physiological serum is close to that of water. Accordingly, to assure a satisfactory consistency of the implant on palpation, the pressure of the physiological serum in the envelope has been increased.
The thin envelope, whose thickness is in the range 0.4 mm to 0.7 mm, is then tensioned by the increased pressure of the physiological serum. The resulting turgidity of the implant obtained in this way reproduces the shape and consistency of the organ it replaces fairly faithfully.
The existence of an increased pressure inside the envelope causes premature aging of the implant. The pressure is seen to reduce progressively due to the effect of migration of the physiological serum through the envelope. The consistency and the shape of the implant therefore deteriorate with time.
The aim of thee invention is to provide a reconstruction implant using a filler liquid whose viscosity is substantially equal to that of water and whose consistency remains close to that of the organ to be replaced.
To this end, the invention consists in a reconstruction implant of predetermined shape, of the aforementioned type, characterized in that the thickness of said envelope is sufficient to confer on said open envelope a shape substantially identical to said predetermined shape in the absence of the filler liquid and in that the pressure of the filler liquid contained in said closed envelope is substantially equal to the pressure outside the envelope.
The particular embodiment of the reconstruction implant has one or more of the following features:
the thickness of the envelope is made such that the ratio of the greatest dimension of the implant to the thickness of the envelope is in the range from 2.3 to 20;
the thickness of the envelope is made such that the ratio of the greatest dimension of the implant to the thickness of the envelope is in the range from 5 to 18;
the envelope includes a silicone membrane whose thickness is greater than 2.5 mm;
the thickness of the envelope is in the range from 2.5 mm to 7.5 mm;
the greatest dimension of the implant is in the range from 2 cm to 5 cm;
the filler liquid is physiological serum;
said predetermined shape is an oval shape and corresponds to the shape, of a testicle.